Context: Family structures can affect the oral health of the child. However, little is known about the impact of the family structure on oral health of children in Africa. Aims: To determine the association between family structure, twice daily toothbrushing, use of fluoridated toothpaste, caries, and oral hygiene status of 5–12-year-old children resident in semi-urban Nigeria. Settings and Design: Secondary analysis of the data of 601 children recruited through a household survey conducted in Ile-Ife, Nigeria. Subjects and Methods: The association between dependent variables (presence of caries, good oral hygiene, use of fluoridated toothpaste, and twice daily toothbrushing) and the family structure (parental structure, number of siblings, and birth rank) was determined. Statistical Analysis Used: Simple and multivariate regression analysis was used to determine the association. The regression models were adjusted for age and gender. Results: Children who were not primogenitor had significantly reduced odds of using fluoridated toothpaste (AOR: 0.91; 95% confidence interval [CI]: 0.85–0.97; P = 0.01) when compared with children who were primogenitors or only children. Furthermore, having 0–2 siblings significantly reduced the odds of having caries (AOR: 0.46; CI: 0.28–0.78; P < 0.001) when compared with children who had three or more siblings. Children who used fluoridated toothpaste had significantly increased odds of having good oral hygiene (AOR: 1.64; 95% CI: 1.18–2.28; P < 0.001). Conclusions: For this study population, the number of siblings and the birth rank increased the chances of having caries and use of fluoridated toothpaste, respectively.

A number of social factors predisposing children and adults to dental caries and poor oral hygiene are being identified. For example, the occupation, education, and income of children's parents can have a significant impact on the children's access to oral health care.[1],[2] In addition, the child's family structure is an important social factor that has a significant impact on the oral health of children, playing a critical role on how the physical and emotional support needed to cope with a disease, its treatment, and its financial burden are provided.[3]

The relationship between family structure and certain health outcomes, especially those affecting adolescents, has been reported in several studies [4],[5] with a number of articles reporting statistically significant associations between family structure and the oral health of adolescents.[6],[7],[8] For example, in the United Kingdom, single mothers and mothers with more than two children are significantly less likely to use dental services than are mothers living with spouses and having not more than two children.[6] Furthermore, children from single parent families are disproportionately affected by caries and low level of use of dental services.[9],[10] Ola et al.[8] had shown that even in an African country, children living with single mothers or without a parent were unlikely to have visited a dentist just as observed in developed countries.

While the differences in the caries status for children from various family structures might have resulted from the families' socioeconomic status and its influence on the child's dietary habits, there are still subtle differences in family structure that may have significant consequences on the oral health of children. Two of these factors include the birth rank of the child and the number of siblings the child has.[11],[12],[13] Studies show that birth rank affects the personality of the individual [14] while others have not.[15] Individual personalities have a significant impact on health.[16] An only child tends to show traits similar to first children [17] and seem to have higher self-esteem than children with siblings.[18] They, just like first children, engaged less in oral health risk behaviors such as smoking, intake of alcohol, and use of psychoactive substances.[19] Zadik [20] found less caries prevalence in first children while Mansbridge [21] did not.

There are also suggestions that the family size increases the risk for child morbidity and mortality as larger family sizes reduce the marginal cost of child quality.[22] Some empirical data, however, suggest that the family size does not have an impact on health.[23],[24] Family size has also been associated with an increased incidence of caries and poor oral health [8],[25],[26] with the risk for caries increasing with increase in the number of siblings.[27],[28]

Unfortunately, very little is known about how the family structure in Africa influences access to dental health services, use of caries prevention practices, and oral hygiene status. Family structures in many African settings differ from those in Europe and America, where most studies on the impact of family structure on health care had been conducted. In Nigeria, a high number (9%) of children live without biological parents.[29] Many children living with guardians do not receive the much needed attention as do biological children living with parents.[30] Learning how family structures in different cultures impact on oral health is, therefore, important.

This study explored the association between family structure (number of siblings, birth rank, and parental structure), oral hygiene practices (twice daily toothbrushing and use of fluoridated toothpaste), caries, and oral hygiene status of children in the mixed dentition stage (aged 5–12 years) in a representative sample of residents in Ife Central Local Government Area (LGA) of Osun State, Nigeria.

Subjects and Methods

This study is a secondary analysis of data collected through a household survey to determine the association between digit sucking and caries. Part of the study data was published elsewhere [31],[32],[33] and included details of the household survey, sample size determination, sampling techniques, and data collection process.

Study design

Data were collected through a cross-sectional study using a household survey because it increased the probability of including children targeted for the study from all the socioeconomic strata in the study population, irrespective of their ability to be enrolled in school or not. Data collection was done during evenings of the weekend of the summer holidays (July to August 2013) when most participants and their parents will likely be home.

Study setting

The semi-urban Ife Central LGA of Osun State was chosen as the study location due to its proximity to Obafemi Awolowo University and Obafemi Awolowo University Teaching Hospitals Complex, the host institutions of the authors. The 1991 census put the population of the LGA at 96,580. The estimated population for 2004 is 138,818, including a child population of 14,000, or about 10% of the total population.

Study population

For this analysis, only children between the ages of 5 and 12 years were included in the study. The lower age limit of 5 years was based on the typical age of the first eruption of permanent dentition in the study population.[34] Only children who were present in the home at the time of the study were eligible to participate in the study.

Sample size determination

Sample size was calculated using the formula by Araoye.[35] The caries prevalence of 13.9%[36] was used for determine the sample size required for this study. The required minimum sample for the study was approximately 200 having adjusted for a margin of error of 5% and a confidence level of 95%. The data of 601 children were accessible for the primary based on this secondary data analysis. The data retrieved for this study are, therefore, adequate.

Sampling technique

Detailed information on the sampling technique for the study had been reported by Kolawole et al.[33] The sampling procedure used was a three-level cluster sampling technique. Stage 1 involved the selection of enumeration sites for data collection by balloting. Stage 2 involved the selection of every third household on each street in randomly selected enumeration sites within the LGA. Stage 3 involved the selection of actual respondents for interview and clinical examination. Only one eligible child in each household was selected to participate in the study in the household.

Data collection

Data were collected through personal interviews using of a structured questionnaire administered by trained field workers. Mothers or surrogate mothers responded to the questions on oral health practices on behalf of children aged 5–7 years, based on evidence that their responses were more accurate than the children.[37] When the mother was unavailable, the fathers completed the questionnaires. Children aged 8–12 years old were directly asked about their oral health practices.

Data retrieved for this study include each child's sociodemographic characteristics (age at last birthday and sex), parental structure (living with mother and father, single parents, or with neither parents), number of siblings, and birth rank. It also retrieved details on oral hygiene practices such as toothbrushing frequency and use of fluoridated toothpaste. These questions had four to seven alternatives. To define acceptable levels of each of the components, the following cutoff points were used: Brushing more than once a day and using fluoridated toothpaste always. Respondents who chose the options “irregularly or never,” “once a week,̶ “a few (2–3) times a week,” or “once a day,” when asked the question on toothbrushing, were classified as not having undertaken caries preventive practices. Those who chose the options, i.e. “quite often,” “seldom,” or “not at all” when asked the question on the use of fluoridated toothpaste were classified as not having undertaken caries preventive practices.[31]

Intraoral examination

All study participants underwent oral examinations in their homes on the day of study visits.[33] They were examined under natural light while sitting, by trained dentists and accompanying field workers, using sterile dental mirrors and probes. Radiographs were not taken in the study. Caries status was determined before the oral hygiene status. Caries diagnosis was based on the recommendation of the WHO Oral Health Survey methods.[38] The caries status was assessed by the use of the decayed, missing, and filled teeth/decayed, missing, and filled teeth (dmft/DMFT) index. Children were classified as having caries present when a tooth was identified as decayed, missing, or filled.

The Simplified Oral Hygiene Index (OHI-S) by Greene and Vermillion [39] was used to determine the oral hygiene status. The OHI-S components, the debris index and calculus index, were obtained based on six numerical determinations representing the amount of debris or calculus found on the facial or lingual surfaces of index teeth 8, 3, 14, 24, 19, and 30 in the permanent dentition and A, E, F, K, O, andPin the primary dentition. The debris and calculus index scores were added and divided by the number of surfaces examined to give the OHI-S score. The oral hygiene was classified as good, fair, or poor when the score ranges were 0.0–1.2, 1.3–3.0, and >3.0, respectively.

Standardization of clinical examiners

Four examiners, who were qualified dentists, undertook a series of calibration exercises to ensure the validity of their evaluations. The exercises included protocol-based training on the WHO criteria for the diagnosis of caries,[38] and the OHI-S index described by Greene and Vermillion.[39] The calibration process and the calibration outcome were reported by Kolawole et al.[33]

Data analysis

All the variables in the data were coded, entered into a computer, analyzed by the use of STATA (version 12.0), and checked for missing values and entry errors. Descriptive analysis was conducted by the use of measures of location and dispersion. Simple and multivariate regression with robust variance estimation was used to derive prevalence ratios with 95% confidence interval (CI).

A hierarchical model was used to manage the variables as this enabled us assess the influence of each variable on the outcome as well as allow for control of the effects if confounder effects on the association. Thus, a stepwise selection was done in the multivariate regression with significance level for removal from model set at 0.2. Factors that could also have a significant impact on the outcomes were also included in the multivariate analysis irrespective of the P value obtained in the simple regression analysis.

For data analysis purposes, age was dichotomized into 5–8 years and 9–12 years. Birth rank was dichotomized into “not primogenitor” and “primogenitor or only child” using the criteria set by Ola et al.[8] The number of siblings was also dichotomized into 0–2 siblings and >3 siblings as used in the study by Ola et al.[8] For the logistic regression analysis, parental structure was also dichotomized to “both parent” and “not both parents.” All respondents who lived with mother only, father only, one parent and one step-parent, and no parents were grouped into “not both parents.” All children were categorized as either having caries or caries free. Oral hygiene status was dichotomized to good and poor (fair and poor) oral hygiene.

Four different outcomes were considered in the analysis and described as follows: (a) “Having used fluoridated toothpastes or not;” (b) “having brushed teeth twice daily or not;” (c) “having caries or not;” and (d) “having good oral hygiene or not.” The first two variables were chosen based on the outcome of the study by Folayan et al.[40] that showed that use of fluoridated toothpaste and toothbrushing twice daily were the most significant factors for reducing caries in children in the study population. Statistical significance was defined as P < 0.05.

Ethical consideration

Ethical approval for the study was obtained from the Research and Ethics Committee of Obafemi Awolowo University Teaching Hospitals Complex, Ile-Ife. Approval for the conduct of the study was obtained from the Local Government Authority, before the commencement of the study. The primary study was conducted in full compliance with the approved protocol and in full accordance with the National Health Research Ethics Code which was developed in accordance with the World Medical Association Declaration of Helsinki and other global bioethics codes. Efforts were made to minimize risks to participants such as the loss of confidentiality and discomfort with the personal nature of questions. Written informed consent was obtained from the parents of all study participants and written assent obtained from all children aged 8–12 years old who participated in the primary study. The consenting process for the primary study was approved by Obafemi Awolowo University Teaching Hospitals Complex, Ile-Ife. Participants in this primary study experienced no direct benefit, and no compensation was paid. However, participants were given token gifts of stationery including pencils, erasers, sharpeners, or a small tube of fluoride-containing toothpaste that did not exceed a value of $0.50.

Results

[Table 1] shows the demographic profile of the study participants. The mean age of the study participants was 7.9 ± (2.2) years and 291 (48.4%) were males. A large number of study participants lived with both parents (88.7%). Furthermore, 190 (31.6%) participants were primogenitors/only child and 7 (1.2%) respondents were not biological children of the family.

Only 23 (3.8%) study participants had visited the dental clinic in the past 12 months, 55 (9.2%) brushed twice daily or more, 187 (31.1%) consumed sugary snacks in between meals less than once a day, and 506 (84.2%) used fluoridated toothpaste always.

Only 89 (14.8%) study participants had caries. The dmft ranged from 0 to 8 with a mean dmft of 0.27 ± (0.85). One hundred and forty-two (90.0%) of the 156 carious primary teeth were unrestored, 11 (7.1%) were extracted, and three (1.9%) were filled. The DMFT ranged from 0 to 4 with a mean DMFT of 0.06 ± (0.38). Twenty-seven (81.8%) of the 33 carious permanent teeth were unrestored, three (9.1%) were extracted, and two (6.1%) were filled.

[Table 2] highlights factors associated with toothbrushing twice daily or more. There was no significant factor associated with twice daily brushing or more in the study population. The odds of brushing twice daily or more reduced for children who were 5–8 years old when compared with those 9–12 years old (PR: 0.69; 95%CI: 0.42–1.14), and for children who were not first primogenitors when compared to those who were primogenitors and only child (PR: 0.64; 95% CI: 0.39–1.07). The odds of brushing twice daily or more increased for males when compared to females (PR: 1.50; 95%CI: 0.90–2.50).

Table 2: Frequency distribution and results of simple and multivariate regression analysis for the association between demographic variables, family structure, and twice daily tooth brushing in a sample of 601 children

[Table 3] highlights the factors associated with the use of fluoridated toothpaste. The only significant predictor was not being a primogenitor: Study participants who were not primogenitors had reduced odds of using fluoridated toothpaste when compared to those who were primogenitors and only child (APR: 0.91; 95% CI 0.85–0.97).

Table 3: Frequency distribution and results of logistic regression analysis for the association between demographic variables, family structure, and use of fluoridated toothpaste in a sample of 601 children

[Table 4] highlights the factors associated with the presence of caries. There were two significant factors associated with the presence of caries. Having 0–2 siblings reduced the odds of having caries when compared with those with three or more siblings (APR: 0.47; CI: 0.28–0.79). Furthermore, brushing the teeth twice daily or more increased the odds of having caries when compared with those who only brushed once daily (APR: 1.72; 9% CI: 1.00–2.95).

Table 4: Frequency distribution and results of logistics regression analysis for the association between demographic variables, family structure and presence of caries in a sample of 601 children

[Table 5] highlights the factors associated with good oral hygiene. Age and use of fluoridated toothpaste were the only significant factors associated with good oral hygiene. Children aged 5–8 years old had increased odds of having good oral hygiene when compared with children aged 9–12 years old (APR: 1.57; 95% CI: 1.27–1.93). Furthermore, children who used fluoridated toothpaste had increased odds of having good oral hygiene when compared with those who did not use fluoridated toothpaste (APR: 1.64; 95% CI: 1.18–2.26). Toothbrushing twice daily or more had no significant association with good oral hygiene (P = 0.84).

Table 5: Frequency distribution and results of logistic regression analysis for the association between demographic variables, family structure, and good oral hygiene in a sample of 601 children

This study presents important information on oral hygiene practices and family structures associated with the presence of caries and good oral hygiene. We identified a family structure-related variable associated with the use of caries prevention methods – not being a primogenitor reduced the probability of using fluoridated toothpaste. We also found a family structure-related variable associated with caries – children who had 0–2 siblings had reduced probability of developing caries. We also found that toothbrushing twice daily or more increased the probability of having caries, whereas the use of fluoridated toothpaste increased the probability of having good oral hygiene.

The findings of this study are important for addressing the long-term oral health care needs of children in the study population. The mixed dentition stage is a time of significant hormonal changes, with associated physical and psychological development of the child.[41] It is a period during which the child commences transition from childhood to adolescence,[42] and a time when children are establishing their independence from parental influence.[43] Their independence has implications for oral health-care practices one of which is the possibility of less supervision of home oral health-care practices such as brushing and flossing teeth, thereby increasing the risk for poor oral hygiene practices.[44] It is also a time when the consumption of sweets, sugary foods, and drinks, predisposing factors to caries, increases.[44] Identifying those family structure-related variables that help promote oral hygiene practices that reduce caries risk in the mix dentition stage will guide the design and implement of public oral health programs and campaigns.

Our study finding indicates that a child's birth rank and the number of siblings (s)he has is associated with the less use of fluoridated toothpaste and the increased risk for caries, respectively. These two variables are possibly linked to the family size. Large families may need to cut down on expenses, including having to buy cheaper toothpaste, leading to an increased risk of developing caries. Past studies had highlighted that the financial and social pressures that come with having large families often has a negative impact on the oral health of children [45] including increased risk for caries.[46]

We also found that toothbrushing twice daily or more increased the probability of having caries while the use of fluoridated toothpaste increased the probability of having good oral hygiene. This finding is paradoxical, and we cannot find a ready explanation this. One possibility is that children who brush twice daily may have been the ones who had had contact with oral health personnel in the past due to the need to manage caries. The habit of toothbrushing twice daily or more may have therefore being instituted to prevent new caries lesion. The associated good oral hygiene associated with the use of fluoridated toothpaste in the absence of an association with toothbrushing is difficult to explain. We plan to explore this finding further.

The study was unable to show an association between parental structure, oral hygiene practices, caries, and oral hygiene status. This is contrary to the findings of a number of reports in the field which had demonstrated this relationship.[46],[47] The small number of children not living with both parents and the small number of children with caries made it difficult to conduct meaningful subanalysis to determine specific forms of parenting structures that may have an impact on caries risk and affect oral hygiene practices. There is little known about the effect of parenting structure on the oral health of children in the study population, especially where we have a significant number of children living with guardians. Onyejaka [48] had shown that in Nigeria, children who live with guardians are left behind with respect to dental service utilization despite interventions. It will be important to conduct a study primarily focus on answering this research question.

This study has limitations. The outcome of analysis of the household survey makes the study finding only generalizable to the study population and cannot be extrapolated to represent Nigeria. It cannot also reflect what happens in other suburban communities in Nigeria considering how diverse and heterogeneous Nigeria is.[49] Furthermore, with a cross-sectional study, it is difficult to ascertain the direction of the established relationships between the variables.

Conclusions

The study highlights that birth rank and number of siblings are significantly associated with caries risk reduction practices and caries risk, respectively. These findings further add to public understanding about how the social context of the lives of children informs their oral health. While it would be an uphill task to try and moderate these factors in an effort to reduce caries risk of children and adolescents with mixed dentition using a public health approach, these factors should help clinicians help identify children at higher risk for caries and thereby manage them appropriately.